Solar Impulse II, piloted by Bertrand Piccard, is taking off this morning from Phoenix, Arizona, heading to Tulsa, Oklahoma.

The trip in the solar-powered airplane will take 17 hours and 50 minutes. Traveling by car would take only 15 hours and 46 minutes. But the point behind this leg of the trip isn’t speed, but efficiency. This is the 11th leg in a round-the-world trip that started last year with the goal of promoting sustainable resource development.

Solar Impulse Route

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Solar Impulse II’s route up until today.

You can watch the flight as it happens in the live stream below, or follow updates on the Solar Impulse website.